It was called "ticket to the world". MPE 094.

Detailed T's & C's below (from my reward email):

TERMS AND CONDITIONS: Passenger must fly on a paid, qualifying United transatlantic or transpacific roundtrip flight between the U.S. and Europe or Asia with fares in F, A, C or D booking class for travel between 10/15/04 and 2/15/05 to earn a free United Economy class Saver Award ticket. Fly an additional qualifying transatlantic or transpacific roundtrip during the same time period and earn a free Saver Award ticket in United Business class on United-operated and marketed flights systemwide. To Qualify: Valid flights must include a transatlantic or transpacific itinerary on flights between the U.S. and Europe or Asia that are operated by United, but not on United-marketed code-share flights operated by other carriers. Not valid on marketed code-share flights of other carriers operated by United. Sydney (SYD) and Melbourne (MEL) are not qualifying destinations for this offer. Travel beyond international gateway or beyond U.S. gateway is permitted when flown on a direct flight operated and marketed by United. This offer is not combinable with other offers and may be earned a maximum of one time. Passengers may not earn both awards. If a passenger travels once within the allotted travel period, then he will earn a free United Economy XY ticket. If a passenger travels twice within the allotted travel period, then he will earn a free United Business XC ticket. Min./Max. Stay Requirements: Per rule of the published fare purchased. Valid Routing: Open jaws are permitted per rules of the published fare purchased as long as all the above conditions are met. Membership Requirements: Offer valid for all Mileage Plus members, where local laws permit. Registration is required by 2/15/05 to be eligible for the offer. Qualifying flights must be posted to the Mileage Plus account in order to qualify for this offer. In case of retroactive crediting of flights, only flights posted by 3/1/05, will be regarded as qualifying flights. Other Restrictions: Promotion is not valid on government or Round-the-World fares. Offer not valid on private or unpublished fares. Offer is subject to change without notice and other restrictions may apply.

Free Economy/Business Award Ticket Terms & Conditions: Free Economy/Business award tickets are valid for qualifying roundtrip travel on any United-operated flight systemwide. Free award tickets can only be booked through United Airlines. Qualifying members will be notified 4–8 weeks after 2/15/05 and booking of the free award flight is only possible after this notification. Valid Travel Dates: The free ticket will be valid for travel between 4/1/05 and 12/31/05, with all travel completed by 12/31/05. Blackout period for free ticket redemption applies between 5/26/05 and 6/20/05. Purchase Requirements: Tickets must be booked at least 14 days in advance. Min./Max. Stay Requirements: None. Valid Routing: No stopovers or circle trips are allowed and destinations are subject to change. Booking Class: United Economy free award ticket is redeemed in XY class and the United Business free award ticket is redeemed in XC class. Seats are limited and may not be available on all flights/dates. If a customer has qualified for a United Business (XC) ticket and seats are not available in XC for the desired flight, the customer may elect to travel in United Economy (XY) if that is available. Transferability: Free award flight is transferable, but the booking of the free award ticket must be made by the member posting the qualifying flights and receiving the notification. Free ticket may not be bartered or sold. Mileage Plus Accrual: Passenger traveling on the free ticket may not accrue Mileage Plus miles or earn miles toward Mileage Plus elite status. Upgradeability: Nonupgradeable. Itinerary Changes: No changes can be made after ticketed departure date for any portion of the ticket. Changes made before departure date are subject to a service charge of $100. Issued tickets may not be refunded for cash or another free award ticket, only taxes will be refunded. Offer is subject to change without notice and other restrictions may apply.

If not stated differently in these terms and conditions, all terms and conditions of Mileage Plus apply. United may change Mileage Plus program rules, regulations, travel awards and special offers, or terminate the Mileage Plus program at any time and without notice. Mileage Plus participation may not be permitted in some countries. United and Mileage Plus are registered service marks.

* Free Ticket Additional Taxes/Fees: Taxes and fees related to the free award travel are the responsibility of the passenger. For award travel, passenger is responsible for the September 11th Security Fee of up to $10 maximum per roundtrip and Passenger Facility Charges of up to $18 depending on itinerary. For U.S. travel, a $3.20 per flight segment tax will also apply; a flight segment is defined as one take-off and one landing. Travel for Alaska and Hawaii does not include a $7 (each way) departure tax. All passengers are responsible for international arrival and departure taxes. For travel from Canada, fares do not include U.S. Inspection fees of $7 per roundtrip, taxes/fees imposed by the Canadian government of up to $19.50 per roundtrip, and a $27.40 per roundtrip international departure and arrival tax if outside of the 225-mile buffer zone. For international travel, passengers originating in the U.S. are responsible for taxes, fees and airport charges of up to $124 depending on destination. For passengers traveling between points outside the U.S., passengers are responsible for any other taxes and fees that may apply. United promotion code: MPE 094